EP2881679B1

EP2881679B1 - Electric heater

Info

Publication number: EP2881679B1
Application number: EP13290298.2A
Authority: EP
Inventors: Jean-Philippe Gries
Original assignee: Mahle Behr France Rouffach SAS
Current assignee: Mahle Behr France Rouffach SAS
Priority date: 2013-12-03
Filing date: 2013-12-03
Publication date: 2017-05-10
Anticipated expiration: 2033-12-03
Also published as: JP2015109274A; CN104703305A; US20150156822A1; EP2881679A1; CN104703305B; US9686823B2

Description

Field of invention

The invention relates to an electric heater for an automobile vehicle, with at least one heating element and with at least one circuit board, whereby the circuit board possesses at least one contact area through which an electrical connection between a heating element and a power supply can be realized, whereas the heating element possesses at least one PTC-heating element.

State of the art

Electric heaters usually consist of at least one heating element which can be heated by applying an electric current to the element. The heat is then transported via fins or other thermally conductive parts to a heat sink. The heat sink can thus be heated by the heating element. To control the electric current on the heating element electric heaters also possess a control unit.
Electric heaters known in the state of the art have a connection assembly between the heating elements and the control unit and/or the power supply. The connection assembly is usually built of a male connector and a female connector. Due to the nature of such a connection assembly the electric heater is exposed to mechanical stress while the connectors are being connected.
Furthermore the connection assembly can be exposed to corrosion, humidity or mechanical stress due to its location within the electric heater. Especially, if the individual heating elements are connected by a connection assembly to a common bus-system, which is connected to a power supply, the assembling of every heating element will cause mechanical stress to all the other already assembled heating elements. This can lead to damage within the connection assemblies or the heating elements.
Furthermore it is difficult to achieve a connection assembly that is sufficiently sealed off against water or more general humidity. Especially the area around the connector in or at a housing is critical, as water or humidity can leak through the joint-area between the connector and the housing.
An entry of water or humidity in general can lead to fretting corrosion and hence to failure of the electric heater. Due to the environment in which such electric heaters are usually used, the connector has to fulfill a high level of requirements over the full lifetime to prevent failure. Electric heaters of this kind are usually used within automobile vehicles to support the heating of the engine or the interior of the vehicle.
Document WO 02/057100 A2 discloses an electric heater for an automobile vehicle, with at least one heating element and with at least one circuit board, whereby the circuit board possesses at least one contact area through which an electrical connection between a heating element and a power supply can be realized, whereas the heating element possesses at least one PTC-heating element, whereby the heating element can be clipped to the circuit board by the means of a connector clip, whereby the connector clip possesses two flexible extensions which are arranged opposed to each other.

Object of the invention, solution, advantages

Therefore it is the object of the invention to provide an electric heater which has an improved connection between a heating element and a circuit board of the electric heater, whereby the connection can be obtained with a minimum of mechanical stress to the electric heater. Furthermore the electric heater should be easily producible.
The object is achieved by the features of patent claim 1.
According to the invention an electric heater for an automobile vehicle is given, with at least one heating element and with at least one circuit board, whereby the circuit board possesses at least one contact area through which an electrical connection between a heating element and a power supply can be realized, whereas the heating element possesses at least one PTC-heating element, whereby the heating element comprises a connector clip by the means of which the heating element can be clipped to the circuit board, whereby the connector clip possesses two flexible extensions, which are arranged opposed to each other.
A connector clip is advantageous as it can be placed on the circuit board without the need for additional tools. Furthermore the clip can be slipped over the circuit board without the need to have big assembly forces. Therefore the mechanical stress for other connections and elements of the circuit board or the electric heater is very limited. The connector clip has two flexible extensions which can be deflected by the circuit board with a reasonable force. The deflection creates a contact pressure, which helps to fix the connector at the circuit board and thus stabilizes the connection. Depending on the material of the flexible extensions the connector can be used to create a physical connection between the heating element and the circuit board and possibly to create an electrical connection between the heating element and the contact area of the circuit board. This helps to reduce the amount of needed parts and reduces the complexity of the electric heater.
The connection of the heating element directly to the circuit board is advantageous as no further elements are needed. Especially bus bars, which are usually connected to all the heating elements of the electric heater, are not needed. The bus bars are usually used to connect the heating elements to a control unit and/or a power supply. By connecting the contact areas of the circuit board directly to a power supply and connecting the heating elements directly to the circuit board, a simpler build-up of the electric heater can be achieved.
According to one advantageous refinement of the invention, the distance between the two flexible extensions is smaller than the height of the plate-shaped circuit board in the zone of the contact area.
Through a distance between the flexible extensions, especially between the closest points of the flexible extensions, which is smaller than the height of the circuit board, a contact pressure between the circuit board and the flexible extensions can be produced by inserting the circuit board in the connector clip. This contact pressure helps to stabilize the connection between the connector clip and the circuit board, as it works against relative movement of the circuit board against the connector clip. According to the invention, the connector clip forms a U-shaped cross-section, which forms a receiving area, whereby the circuit board is inserted into the receiving area.
The U-shaped cross-section is beneficial as it provides an opening through which the circuit board is inserted in the connector clip. The flanks of the U-shaped cross-section are formed by the flexible extensions. The U-shaped cross-section can be expanded by a deflection of the flexible extensions away from each other or narrowed by a deflection of the flexible extensions towards each other. The deflection of the flexible extensions depends predominantly on the height of the plate-shaped circuit board. The circuit board preferably has a height between 0,5 mm and 2 mm, whereby the height is most preferably between 1 mm and 1,6 mm. A bigger height of the circuit board results In a bigger deflection whereas a smaller height results in a smaller deflection.
The flexible extensions can have an arched cross-section. The arched design can help the process of inserting the circuit board in the receiving area, as the arched design creates an opening at the top of the U-shaped cross-section, which narrows down with a growing distance from the opening. Besides that the arched design creates a contact pressure transmitting area which is much smaller than the cross-section area of complete receiving area. This results in a higher contact force in the contact pressure transmitting area.
It is preferable, if a force is created by the insertion of the circuit board into the receiving area of the connector clip, the force creates contact pressure between the contact area and the flexible extensions.
Through such a force the stability of the connection between the connector clip and the circuit board can be improved as the contact pressure between the connector clip and the circuit board works against any relative movement between the connector clip and the circuit board. Thus higher forces are needed to pull the connector clip away from the circuit board, which makes an unintentional release unlikely.
Furthermore it is functional, if at least one of the flexible extensions is electrically conductive. This is advantageous as the electrical connection between the heating element and the contact area or between the PTC-heating element and the contact area can be achieved directly through the connector clip. This is beneficial as no additional parts are needed.
Besides this it is preferable, if the PTC-heating element is electrically connectable to the contact area by the heating element and/or the connector clip.
The PTC-heating element can either be connected to the connector clip by the heating element itself which can have electrically conductive capabilities or by an additional element such as an electric bridge or a cable. Through this electrical connection it is possible to connect the PTC-heating element to a power supply. By applying an electrical current to the PTC-heating element heat can be generated, which can be radiated from the PTC-heating elements and/or the heat transmitting fins and/or the heating element.
Furthermore it is beneficial, if the contact area of the circuit board is coated with an electrically conductive material. An electrically conductive material can be for instance tin, copper, brass, silver, an alloy of the afore mentioned or the like. A coating of the contact area and the connector clip with an identical electronically conductive coating is especially advantageous to reach a better material compatibility between the involved elements. Especially the connector clip can be made from or coated with a conductive material like the before mentioned materials.
In an additional embodiment it is preferable, if the contact area and/or the circuit board and/or the connector clip is covered by an electrical insulation and/or an insulation against fluid leakage and/or an insulation against mechanical stress.
An insulation against short-circuits, fluid leakage or mechanical stress is advantageous to prevent failures. Insulations of these kinds can for instance be realized by membranes or foils, which are spread over the specific area. An insulation can be installed on the circuit board especially after the connector clips have been connected to the circuit board. The insulation can advantageously cover the contact area as well as the connector clips. This results in a better insulation against humidity or short-circuits in the area of the electrical contact between the circuit board and the connector clip.
Besides this it is preferable, if the circuit board and/or the contact area of the circuit board is electrically connected to at least one pole of a power supply.
Via a connection between the circuit board and a pole of a power supply the power supply of the heating element or more specific the power supply of the PTC-heating element can be realized. In a preferable embodiment the contact area is electrically connected to the connector clip, while the connector clip is either electrically connected to the PTC-heating element itself or to the heating element, which in turn can be electrically connected to the PTC-heating element. In an advantageous embodiment of the invention the PTC-heating elements are connected to at least one pole of a power supply by one heating element and furthermore connected to a second pole of a power supply or to the ground by a second heating element, which is adjacent to it, to create a closed circuit, which allows the PTC-heating elements to be heated.
The connection between the PTC-heating element and the poles of the power supply can be realized through electrically conductive elements such as the heat transmitting fins or the heating elements or additional conductive elements such as bridges or cables.
Furthermore it is preferable, if the circuit board is encased partially or in full extent in a housing. A housing, preferably a waterproof housing, is beneficial to create an insulated environment around the circuit board. The housing can encase only the part of the circuit board where the contact areas are located or in an alternative the complete circuit board. Preferably the whole circuit board is encased by the housing. In a preferred embodiment the housing encases the connector clips of the heating elements as well. Such a housing can prevent electric short-circuits and/or fretting corrosion due to humidity. The openings in the housing, which are needed for the heating elements, can be sealed by conventional seals, which are known in the state of the art.
In another embodiment it is favorable, if the heating element is a planar body which extensions in two of the three spatial directions are larger than the extension in the third spatial direction, whereby the PTC-heating element is connected to one side of the heating element and one or more fins are connected to the opposed side of the heating element.
Such a design of the heating element is advantageous as it allows a multitude of PTC-heating elements to be placed alongside each heating element. Due to its relatively short extension in the third spatial direction the temperature resistance along the third spatial direction is relatively low, which helps to improve the overall efficiency of the electric heater. An alternative embodiment can be characterized by PTC-heating elements on both of the opposing sides of the heating. The heat transmitting fins can thereby be placed between the PTC-heating elements and/or directly on top of the PTC-heating elements.
Further preferable embodiments of the invention are described in the claims and the following description of the drawings.

Description of the drawings

The invention is explained in detail below by means of an exemplary embodiment and with reference to the drawings, in which;

Fig.1: shows a circuit board with a multitude of contact areas that are electrically connected to a power supply, whereby two heating elements are shown next to the circuit board, whereby each heating element shows one connector clip through which the heating elements can be connected to the circuit board, and
Fig. 2: shows the embodiment of figure 1, whereby the heating elements are connected to the circuit board by means of the connector clips.

Preferred embodiments of the invention

Figure 1 shows an electric heater 1 with one circuit board 2 and two heating elements 4. Each heating element 4 possesses a multitude of heat transmitting fins 5 and at least one PTC-heating element (not shown in figure 1). Each heating element 4 further shows a connector clip 6, which can be used to connect the heating element 4 to the circuit board 2.
The circuit board 2 possesses a multitude of contact areas 3. These contact areas 3 are connected to a power supply that is not shown in figure 1. The connection between the contact areas 3 and the power supply can be realized by conducting paths and power switches on the circuit board 2. The circuit board 2 can be a printed circuit board as it is widely known in the state of the art.
The contact areas 3 are located near to one of the edges of the circuit board so that they can easily be covered by the connector clips 6 of the heating elements 4. To cover the contact areas 3 with the connecter clips 6, the connector clips 6 can be plugged over the edge of the circuit board 2 in a way that one of the flexible extensions 7 slips over the circuit board 2 and the other flexible extension 7 slips under the circuit board 2. The flexible extensions 7 in figure 1 are arched. The tips of the flexible extensions 7 point away from each other. This design of the connector clip 6 makes it easier to slip the connector clip 6 over the circuit board 2.
The deflection of the flexible extensions 7, which is caused by the circuit board 2 as it has a height that is bigger than the smallest distance between the flexible extensions 7 of one connector clip 6, creates a force that is directed at the circuit board 2 and that creates a contact pressure between the flexible extensions 7 and the circuit board 2. This contact pressure helps to avoid relative movement between the circuit board 2 and the connector clip 6 and thus stabilizes the connection.
Each connector clip 6 can be attached to the circuit board 2 in a way that only one contact area 3 is covered by one connector clip 6. This makes it possible to create a specified electrical connection between one certain contact area 3 and one connector clip 6. As the circuit board 2 preferably either is a control unit or is connected to a control unit it is possible to activate or deactivate the heating elements 4 individually.
The circuit board 2 can possess contact areas 3 on the upper side, as shown in figure 1, and on the lower side. Depending on the conducting paths on the circuit board 2 the contact area/areas 3, that are connected with one specific connector clip 6, can be connected to one pole of a power supply or to two poles (one contact area relative to one connector relative to one pole). Especially if the contact areas 3 are connected to two different poles of a power supply it is easy to create a closed electric circuit that contains the power supply, the conducting paths, the contact areas 3, the connector clip 6, the heating element 4 and the PTC-heating elements, which are arranged alongside the heating element 4 (not shown in figure 1). Through a closed electric circuit a PTC-heating element can be operated in a way that heat is produced. In a still further refinement the heating elements or more specific the PTC-heating elements can be connected to a power supply by further additional means, such as cables or conductive bridge elements.
To plug the connector clips 6 to the circuit board 2 the heating elements 4 must be moved in a direction, which is indicated by the arrow that is marked with the reference number 8.
Figure 2 shows the embodiment of figure 1, whereby the heating elements 4 are connected to the circuit board 2. The connection is created by a lateral movement of the heating elements 4 along the direction 8 of figure 1. The connector clips 6 are slipped over the right edge of the circuit board 2. The connector clips 6 embrace the circuit board 2 with the flexible extensions 7. The deflected flexible extensions 7 create a force, which results in a contact pressure between the flexible extensions 7 and the circuit board 2. In an alternative embodiment a multitude of heating elements 4 can be applied to the circuit board. A preferred embodiment has one heating element 4 attached to each contact area 3.
An electric heater can possess a multitude of circuit boards, which can be connected to each other by additional wiring or a circuit board with a multitude of busbars, which are connected to the negative pole and/or the positive pole of a power supply and can be plugged into those connector clips. The system can be arranged within a frame or a housing. It is preferred if the circuit board 2 is covered with an insulation against humidity and/or mechanical stress and/or electric short-circuits. Such means are not shown in the figures 1 and 2. In another preferred embodiment the circuit board and/or the connector clips are encased in a waterproof housing. Preferably the whole circuit board and especially the area where the electrical connection between the heating elements and the circuit board is created is encased in the housing. This helps to prevent short-circuits and damage due to corrosion. Such a housing is not shown in the figures 1 and 2.
While the invention has been shown in the figures 1 and 2 in one preferred embodiment, it will be clear to those skilled in the arts to which it pertains that a variety of modifications and changes can be made thereto without departing from the scope of the claims.

Claims

Electric heater (1) for an automobile vehicle, with at least one heating element (4) and with at least one circuit board (2), whereby the circuit board (2) possesses at least one contact area (3) through which an electrical connection between a heating element (4) and a power supply can be realized, whereas the heating element (4) possesses at least one PTC-heating element, wherein the heating element comprises a connector clip (6) by the means of which the heating element (4) can be clipped to the circuit board (3), whereby the connector clip (6) possesses two flexible extensions (7), which are arranged opposed to each other, whereby the connector clip (6) forms a U-shaped cross-section, which forms a receiving area, whereby the circuit board (2) is inserted into the receiving area.
Electric heater (1) as claimed in claim 1, characterized in that the distance between the two flexible extensions (7) is smaller than the height of the plate-shaped circuit board (2) in the zone of the contact area (3).
Electric heater (1) as claimed in claim 2, characterized in that a force is created by the insertion of the circuit board (2) into the receiving area of the connector clip (6), whereby the force creates contact pressure between the contact area (3) and the flexible extensions (7).
Electric heater (1) as claimed in one or more of the previous claims, characterized in that at least one of the flexible extensions (7) is electrically conductive.
Electric heater (1) as claimed in one or more of the previous claims, characterized in that the PTC-heating element is electrically connectable to the contact area (3) by the heating element (4) and/or the connector clip (6).
Electric heater (1) as claimed in one or more of the previous claims, characterized in that the contact area (3) and/or the circuit board (2) and/or the connector clip (6) is covered by an electrical insulation and/or an insulation against fluid leakage and/or an insulation against mechanical stress.
Electric heater (1) as claimed in one or more of the previous claims, characterized in that the circuit board (2) and/or the contact area (3) of the circuit board (2) is electrically connected to at least one pole of a power supply.
Electric heater (1) as claimed in one or more of the previous claims, characterized in that the circuit board (2) is encased in a housing partially or in full extent.
Electric heater (1) as claimed in one or more of the previous claims, characterized in that the heating element (4) is a planar body which extensions in two of the three spatial directions are larger than the extension in the third spatial direction, whereby the PTC-heating element is connected to one side of the heating element (4) and the heating element comprises one or more fins (5) which are connected to the opposed side of the heating element (4).